Problem: Luis bought a new pair of glasses at the store when they were having a $25\%$ off sale. If the regular price of the pair of glasses was $$21$, how much did Luis pay with the discount?
First, find the amount of the discount by multiplying the original price of the of the item by the discount. $$21$ $\times$ $25\%$ $=$ Percent means "out of one hundred," so $25\%$ is equivalent to $\frac{25}{100}$ which is also equal to $25 \div 100$ $25 \div 100 = 0.25$ Multiply the discount you just converted into a decimal by the original price to find the amount of money saved. $0.25$ $\times$ $$21$ $ = $ $$5.25$ Subtract the discount you just found from the original price to get the final price Luis paid. $$21$ $-$ $$5.25$ $ = $ $$15.75$ Luis paid $$15.75$ for the pair of glasses.